Inhibition of mitochondrial permeability transition pore opening: the Holy Grail of cardioprotection. Basic Res Cardiol. 2010;105:151-154. [PMID: 20066536 DOI: 10.1007/s00395-009-0080-9]

Activation of the nonneuronal cholinergic cardiac system by hypoxic preconditioning protects isolated adult cardiomyocytes from hypoxia/reoxygenation injury

Activation of the vagus nerve mediates cardioprotection and attenuates myocardial ischemia/reperfusion (I/R) injury. In response to vagal activation, acetylcholine (ACh) is released from the intracardiac nervous system (ICNS) and activates intracellular cardioprotective signaling cascades. Recently, however, a nonneuronal cholinergic cardiac system (NNCCS) in cardiomyocytes has been described as an additional source of ACh. To investigate whether the NNCCS mediates cardioprotection in the absence of vagal and ICNS activation, we used a reductionist approach of isolated adult rat ventricular cardiomyocytes without neuronal cells, using hypoxic preconditioning (HPC) as a protective stimulus. Adult rat ventricular cardiomyocytes were isolated, the absence of neuronal cells was confirmed, and HPC was induced by 10/20 min hypoxia/reoxygenation (H/R) before subjection to 30/5 min H/R to simulate I/R injury. Cardiomyocyte viability was assessed by trypan blue staining at baseline and after HPC+H/R or H/R. Intra- and extracellular ACh was quantified using liquid chromatography-coupled mass spectrometry at baseline, after HPC, after hypoxia, and after reoxygenation, respectively. In a subset of experiments, muscarinic and nicotinic ACh receptor (m- and nAChR) antagonists were added during HPC or during H/R. Cardiomyocyte viability at baseline (69 ± 4%) was reduced by H/R (10 ± 3%). With HPC, cardiomyocyte viability was preserved after H/R (25 ± 6%). Intra- and extracellular ACh increased during hypoxia; HPC further increased both intra- and extracellular ACh (from 0.9 ± 0.7 to 1.5 ± 1.0 nmol/mg; from 0.7 ± 0.6 to 1.1 ± 0.7 nmol/mg, respectively). The addition of mAChR and nAChR antagonists during HPC had no impact on HPC's protection; however, protection was abrogated when antagonists were added during H/R (cardiomyocyte viability after H/R: 23 ± 5%; 13 ± 4%). In conclusion, activation of the NNCCS is involved in cardiomyocyte protection; HPC increases intra- and extracellular ACh during H/R, and m- and nAChRs are causally involved in HPC's cardiomyocyte protection during H/R. The interplay between upstream ICNS activation and NNCCS activation in myocardial cholinergic metabolism and cardioprotection needs to be investigated in future studies.NEW & NOTEWORTHY The intracardiac nervous system is considered to be involved in ischemic conditioning's cardioprotection through the release of acetylcholine (ACh). However, we demonstrate that hypoxic preconditioning (HPC) protects from hypoxia/reoxygenation injury and increases intra- and extracellular ACh during hypoxia in isolated adult ventricular rat cardiomyocytes. HPC's protection involves cardiomyocyte muscarinic and nicotinic ACh receptor activation. Thus, besides the intracardiac nervous system, a nonneuronal cholinergic cardiac system may also be causally involved in cardiomyocyte protection by ischemic conditioning.

Mitochondrial Kinase Signaling for Cardioprotection

Myocardial ischemia/reperfusion injury is reduced by cardioprotective adaptations such as local or remote ischemic conditioning. The cardioprotective stimuli activate signaling cascades, which converge on mitochondria and maintain the function of the organelles, which is critical for cell survival. The signaling cascades include not only extracellular molecules that activate sarcolemmal receptor-dependent or -independent protein kinases that signal at the plasma membrane or in the cytosol, but also involve kinases, which are located to or within mitochondria, phosphorylate mitochondrial target proteins, and thereby modify, e.g., respiration, the generation of reactive oxygen species, calcium handling, mitochondrial dynamics, mitophagy, or apoptosis. In the present review, we give a personal and opinionated overview of selected protein kinases, localized to/within myocardial mitochondria, and summarize the available data on their role in myocardial ischemia/reperfusion injury and protection from it. We highlight the regulation of mitochondrial function by these mitochondrial protein kinases.

Myocardial Ischemia-Reperfusion Injury: Unraveling Pathophysiology, Clinical Manifestations, and Emerging Prevention Strategies

Myocardial ischemia-reperfusion injury (MIRI) remains a challenge in the context of reperfusion procedures for myocardial infarction (MI). While early revascularization stands as the gold standard for mitigating myocardial injury, recent insights have illuminated the paradoxical role of reperfusion, giving rise to the phenomenon known as ischemia-reperfusion injury. This comprehensive review delves into the intricate pathophysiological pathways involved in MIRI, placing a particular focus on the pivotal role of endothelium. Beyond elucidating the molecular intricacies, we explore the diverse clinical manifestations associated with MIRI, underscoring its potential to contribute substantially to the final infarct size, up to 50%. We further navigate through current preventive approaches and highlight promising emerging strategies designed to counteract the devastating effects of the phenomenon. By synthesizing current knowledge and offering a perspective on evolving preventive interventions, this review serves as a valuable resource for clinicians and researchers engaged in the dynamic field of MIRI.

Pharmaceutical Manipulation of Mitochondrial F0F1-ATP Synthase Enables Imaging and Protection of Myocardial Ischemia/Reperfusion Injury Through Stress-induced Selective Enrichment

To rescue ischemic myocardium from progressing to myocardial infarction, timely identification of the infarct size and reperfusion is crucial. However, fast and accurate identification, as well as the targeted protection of injured cardiomyocytes following ischemia/reperfusion (I/R) injury, remain significantly challenging. Here, a near infrared heptamethine dye IR-780 is shown that has the potential to quickly monitor the area at risk following I/R injury by selectively entering the cardiomyocytes of the at-risk heart tissues. Preconditioning with IR-780 or timely IR-780 administration before reperfusion significantly protects the heart from ischemia and oxidative stress-induced cell death, myocardial remodeling, and heart failure in both rat and pig models. Furthermore, IR-780 can directly bind to F0F1-ATP synthase of cardiomyocytes, rapidly decrease the mitochondrial membrane potential, and subsequently slow down the mitochondrial energy metabolism, which induces the mitochondria into a "quiescent state" and results in mitochondrial permeability transition pore inhibition by preventing mitochondrial calcium overload. Collectively, the findings show the feasibility of IR-780-based imaging and protection strategy for I/R injury in a preclinical context and indicate that moderate mitochondrial function depression is a mode of action that can be targeted in the development of cardioprotective reagents.

The interplay between H19 and HIF-1α in mitochondrial dysfunction in myocardial infarction

Myocardial infarction(MI) causes prolonged ischemia of infarcted myocardial tissue, which triggers a wide range of hypoxia cellular responses in cardiomyocytes. Emerging evidence has indicated the critical roles of long non-coding RNAs(lncRNAs) in cardiovascular diseases, including MI. The purpose of this study was to investigate the roles of lncRNA H19 and H19/HIF-1α pathway during MI. Results showed that cell injury and mitochondrial dysfunction were induced in hypoxia-treated H9c2 cells, accompanied by an increase in the expression of H19. H19 silencing remarkably diminishes cell injury, inhibits the dysfunctional degree of mitochondria, and decreases the injury of MI rats. Bioinformatics analysis and dual-luciferase assays revealed that H19 was the hypoxia-responsive lncRNA, and HIF-1α induced H19 transcription through direct binding to the H19 promoter. Moreover, H19 participates in the HIF-1α pathway by stabilizing the HIF-1α protein. These results indicated that H19 might be a potential biomarker and therapeutic target for myocardial infarction.

The role and mechanisms of microvascular damage in the ischemic myocardium

Following myocardial ischemic injury, the most effective clinical intervention is timely restoration of blood perfusion to ischemic but viable myocardium to reduce irreversible myocardial necrosis, limit infarct size, and prevent cardiac insufficiency. However, reperfusion itself may exacerbate cell death and myocardial injury, a process commonly referred to as ischemia/reperfusion (I/R) injury, which primarily involves cardiomyocytes and cardiac microvascular endothelial cells (CMECs) and is characterized by myocardial stunning, microvascular damage (MVD), reperfusion arrhythmia, and lethal reperfusion injury. MVD caused by I/R has been a neglected problem compared to myocardial injury. Clinically, the incidence of microvascular angina and/or no-reflow due to ineffective coronary perfusion accounts for 5-50% in patients after acute revascularization. MVD limiting drug diffusion into injured myocardium, is strongly associated with the development of heart failure. CMECs account for > 60% of the cardiac cellular components, and their role in myocardial I/R injury cannot be ignored. There are many studies on microvascular obstruction, but few studies on microvascular leakage, which may be mainly due to the lack of corresponding detection methods. In this review, we summarize the clinical manifestations, related mechanisms of MVD during myocardial I/R, laboratory and clinical examination means, as well as the research progress on potential therapies for MVD in recent years. Better understanding the characteristics and risk factors of MVD in patients after hemodynamic reconstruction is of great significance for managing MVD, preventing heart failure and improving patient prognosis.

Mechanism of heart failure after myocardial infarction

Despite the widespread use of early revascularization and drugs to regulate the neuroendocrine system, the impact of such measures on alleviating the development of heart failure (HF) after myocardial infarction (MI) remains limited. Therefore, it is important to discuss the development of new therapeutic strategies to prevent or reverse HF after MI. This requires a better understanding of the potential mechanisms involved. HF after MI is the result of complex pathophysiological processes, with adverse ventricular remodeling playing a major role. Adverse ventricular remodeling refers to the heart's adaptation in terms of changes in ventricular size, shape, and function under the influence of various regulatory factors, including the mechanical, neurohormonal, and cardiac inflammatory immune environments; ischemia/reperfusion injury; energy metabolism; and genetic correlation factors. Additionally, unique right ventricular dysfunction can occur secondary to ischemic shock in the surviving myocardium. HF after MI may also be influenced by other factors. This review summarizes the main pathophysiological mechanisms of HF after MI and highlights sex-related differences in the prognosis of patients with acute MI. These findings provide new insights for guiding the development of targeted treatments to delay the progression of HF after MI and offering incremental benefits to existing therapies.

Regulatory effects of trimetazidine in cardiac ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury is a tissue damage during reperfusion after an ischemic condition. I/R injury is induced by pathological cases including stroke, myocardial infarction, circulatory arrest, sickle cell disease, acute kidney injury, trauma, and sleep apnea. It can lead to increased morbidity and mortality in the context of these processes. Mitochondrial dysfunction is one of the hallmarks of I/R insult, which is induced via reactive oxygen species (ROS) production, apoptosis, and autophagy. MicroRNAs (miRNAs, miRs) are non-coding RNAs that play a main regulatory role in gene expression. Recently, there are evidence, which miRNAs are the major modulators of cardiovascular diseases, especially myocardial I/R injury. Cardiovascular miRNAs, specifically miR-21, and probably miR-24 and miR-126 have protective effects on myocardial I/R injury. Trimetazidine (TMZ) is a new class of metabolic agents with an anti-ischemic activity. It has beneficial effects on chronic stable angina by suppressing mitochondrial permeability transition pore (mPTP) opening. The present review study addressed the different mechanistic effects of TMZ on cardiac I/R injury. Online databases including Scopus, PubMed, Web of Science, and Cochrane library were assessed for published studies between 1986 and 2021. TMZ, an antioxidant and metabolic agent, prevents the cardiac reperfusion injury by regulating AMP-activated protein kinase (AMPK), cystathionine-γ-lyase enzyme (CSE)/hydrogen sulfide (H2S), and miR-21. Therefore, TMZ protects the heart against I/R injury by inducing key regulators such as AMPK, CSE/H2S, and miR-21.

Madder (Rubia cordifolia L.) Alleviates Myocardial Ischemia-Reperfusion Injury by Protecting Endothelial Cells from Apoptosis and Inflammation

Objective

Ischemia-reperfusion injury often occurs in organ transplantation, coronary heart disease, ischemic heart disease, and other diseases, which greatly reduces clinical efficacy. This study examined the effectiveness of madder as a medicine to treat ischemia-reperfusion injury.

Methods

The efficacy of madder was evaluated by measuring myocardial infarction size, coronary outflow volume, myocardial contraction rate, activation of inflammatory factors, autophagy factors, apoptosis factors, and related pathway genes in mice.

Results

The results indicated that treatment with madder can effectively reduce the area of myocardial infarction and restore arterial blood flow velocity and myocardial contractility in mice. Additionally, madder treatment inhibited the expression of inflammatory factors, autophagy factors, and apoptosis factors in mice and reduced the degree of myocardial cell injury. Studies have also shown that madder treatment can alleviate myocardial ischemia-reperfusion injury in mice and inhibit the occurrence of inflammatory response by inhibiting the activity of the NF-κB pathway.

Conclusion

The results showed that madder was effective against ischemia-reperfusion injury, thus showing potential as a clinical drug for treating ischemia-reperfusion injury.

Advances in research on the protective mechanisms of traditional Chinese medicine (TCM) in myocardial ischaemia-reperfusion injury

CONTEXT

Developing effective drugs to treat myocardial ischaemia-reperfusion (MI/R) injury is imperative. Traditional Chinese medicines (TCMs) have had considerable success in the treatment of cardiovascular diseases. Elucidating the mechanisms by which TCMs improve MI/R injury can supplement the literature on MI/R prevention and treatment.

OBJECTIVE

To summarise TCMs and their main protective mechanisms against MI/R injury reported over the past 40 years.

METHODS

Relevant literature published between 1980 and 2020 in Chinese and English was retrieved from the Web of Science, PubMed, SpringerLink, PubMed Central, Scopus, and Chinese National Knowledge Infrastructure (CNKI) databases. Search terms included 'medicinal plants', 'myocardial ischaemia reperfusion injury', 'Chinese medicine prescriptions', 'mechanisms', 'prevention', 'treatment' and 'protection'. For inclusion in the analysis, medicinal plants had to be searchable in the China Medical Information Platform and Plant Database.

RESULTS

We found 71 medicinal species (from 40 families) that have been used to prevent MI/R injury, of which Compositae species (8 species) and Leguminosae species (7 species) made up the majority. Most of the effects associated with these plants are described as antioxidant and anti-inflammatory. Furthermore, we summarised 18 kinds of Chinese compound prescriptions, including the compound Danshen tablet and Baoxin pill, which mainly reduce oxidative stress and regulate mitochondrial energy metabolism.

DISCUSSION AND CONCLUSIONS

We summarised TCMs that protect against MI/R injury and their pharmacological mechanisms. This in-depth explanation of the roles of TCMs in MI/R injury protection provides a theoretical basis for the research and development of TCM-based treatment drugs.

Research Progress of Chinese Medicine in the Treatment of Myocardial Ischemia-Reperfusion Injury

Vascular recanalization is the essential procedure in which severe coronary artery stenosis is diagnosed. However, the blood flow recovery associated with this procedure may cause myocardial ischemia-reperfusion injury (MIRI), which aggravates heart failure. Unfortunately, the mechanism of MIRI has historically been poorly understood. As we now know, calcium overloading, oxidative stress, mitochondrial dysfunction, inflammatory responses, and ferroptosis take part in the process of MIRI. Modern medicine has shown through clinical studies its own limited effects in the case of MIRI, whereas Chinese traditional medicine demonstrates a strong vitality. Multiple-target effects, such as anti-inflammatory, anti-oxidant, and cardio-protection effects, are central to this vitality. In our clinic center, Yixin formula is commonly used in patients with MIRI. This formula contains Astragalus, Ligusticum Wallichii, Salvia, Rhodiola Rosea, Radix Angelicae Sinensis, Cyperus Rotundus, and Cassia Twig. Its effects include warming yang energy, activating blood circulation, and eliminating blood stasis. In our previous laboratory studies, we have proved that it can reduce MIRI and oxidative stress injury in rats suffering from ischemia myocardiopathy. It can also inhibit apoptosis and protect myocardium. In this paper, we review the research of Yixin formula and other related herbal medicines in MIRI therapy.

Platelet Membrane-Encapsulated MSNs Loaded with SS31 Peptide Alleviate Myocardial Ischemia-Reperfusion Injury

Clinically, antioxidant therapy is a potential strategy for myocardial ischemia-reperfusion injury (MI/RI), a common complication of acute myocardial ischemia. The H-D-Arg-Dmt-Ly-Phe-NH2 (SS31) peptide is shown to have amazing antioxidant properties, but its utilization is limited by the peptide characteristics, such as the destruction by proteases and rapid metabolism. Silica nanoparticles (MSNs) comprise an excellent material for peptide delivery, owing to the protection effect relating to peptides. Moreover, platelet membrane (PLTM) is shown to be advantageous as a coat for nanosystems because of its specific protein composition, such that a PLTM-coated nanosystem has a stealth effect in vivo, able to target injury in the cardiovascular system. Based on this feature, we designed and prepared a novel nanocarrier to target SS31 delivery. This carrier is encapsulated by a platelet membrane and loaded with SS31 peptide into MSNs. The results reveal that this delivery system can target SS31 to the injured cardiovascular site, exert antioxidant function, and alleviate MI/RI.

Amelioration of myocardial ischemia/reperfusion injury in diabetes: A narrative review of the mechanisms and clinical applications of dexmedetomidine

Mechanisms contributing to the pathogenesis of myocardial ischemia-reperfusion (I/R) injury are complex and multifactorial. Many strategies have been developed to ameliorate myocardial I/R injuries based on these mechanisms. However, the cardioprotective effects of these strategies appear to diminish in diabetic states. Diabetes weakens myocardial responses to therapies by disrupting intracellular signaling pathways which may be responsible for enhancing cellular resistance to damage. Intriguingly, it was found that Dexmedetomidine (DEX), a potent and selective α2-adrenergic agonist, appears to have the property to reverse diabetes-related inhibition of most intervention-mediated myocardial protection and exert a protective effect. Several mechanisms were revealed to be involved in DEX’s protection in diabetic rodent myocardial I/R models, including PI3K/Akt and associated GSK-3β pathway stimulation, endoplasmic reticulum stress (ERS) alleviation, and apoptosis inhibition. In addition, DEX could attenuate diabetic myocardial I/R injury by up-regulating autophagy, reducing ROS production, and inhibiting the inflammatory response through HMGB1 pathways. The regulation of autonomic nervous function also appeared to be involved in the protective mechanisms of DEX. In the present review, the evidence and underlying mechanisms of DEX in ameliorating myocardial I/R injury in diabetes are summarized, and the potential of DEX for the treatment/prevention of myocardial I/R injury in diabetic patients is discussed.

Migraine-Associated Mutation in the Na,K-ATPase Leads to Disturbances in Cardiac Metabolism and Reduced Cardiac Function

Background Mutations in ATP1A2 gene encoding the Na,K-ATPase α2 isoform are associated with familial hemiplegic migraine type 2. Migraine with aura is a known risk factor for heart disease. The Na,K-ATPase is important for cardiac function, but its role for heart disease remains unknown. We hypothesized that ATP1A2 is a susceptibility gene for heart disease and aimed to assess the underlying disease mechanism. Methods and Results Mice heterozygous for the familial hemiplegic migraine type 2-associated G301R mutation in the Atp1a2 gene (α2+/G301R mice) and matching wild-type controls were compared. Reduced expression of the Na,K-ATPase α2 isoform and increased expression of the α1 isoform were observed in hearts from α2+/G301R mice (Western blot). Left ventricular dilation and reduced ejection fraction were shown in hearts from 8-month-old α2+/G301R mice (cardiac magnetic resonance imaging), and this was associated with reduced nocturnal blood pressure (radiotelemetry). Cardiac function and blood pressure of 3-month-old α2+/G301R mice were similar to wild-type mice. Amplified Na,K-ATPase-dependent Src kinase/Ras/Erk1/2 (p44/42 mitogen-activated protein kinase) signaling was observed in hearts from 8-month-old α2+/G301R mice, and this was associated with mitochondrial uncoupling (respirometry), increased oxidative stress (malondialdehyde measurements), and a heart failure-associated metabolic shift (hyperpolarized magnetic resonance). Mitochondrial membrane potential (5,5´,6,6´-tetrachloro-1,1´,3,3´-tetraethylbenzimidazolocarbocyanine iodide dye assay) and mitochondrial ultrastructure (transmission electron microscopy) were similar between the groups. Proteomics of heart tissue further suggested amplified Src/Ras/Erk1/2 signaling and increased oxidative stress and provided the molecular basis for systolic dysfunction in 8-month-old α2+/G301R mice. Conclusions Our findings suggest that ATP1A2 mutation leads to disturbed cardiac metabolism and reduced cardiac function mediated via Na,K-ATPase-dependent reactive oxygen species signaling through the Src/Ras/Erk1/2 pathway.

Applications of tetrahedral DNA nanostructures in wound repair and tissue regeneration

Tetrahedral DNA nanostructures (TDNs) are molecules with a pyramidal structure formed by folding four single strands of DNA based on the principle of base pairing. Although DNA has polyanionic properties, the special spatial structure of TDNs allows them to penetrate the cell membrane without the aid of transfection agents in a caveolin-dependent manner and enables them to participate in the regulation of cellular processes without obvious toxic side effects. Because of their stable spatial structure, TDNs resist the limitations imposed by nuclease activity and innate immune responses to DNA. In addition, TDNs have good editability and biocompatibility, giving them great advantages for biomedical applications. Previous studies have found that TDNs have a variety of biological properties, including promoting cell migration, proliferation and differentiation, as well as having anti-inflammatory, antioxidant, anti-infective and immune regulation capabilities. Moreover, we confirmed that TDNs can promote the regeneration and repair of skin, blood vessels, muscles and bone tissues. Based on these findings, we believe that TDNs have broad prospects for application in wound repair and regeneration. This article reviews recent progress in TDN research and its applications.

A computational model of cardiomyocyte metabolism predicts unique reperfusion protocols capable of reducing cell damage during ischemia/reperfusion

If a coronary blood vessel is occluded and the neighboring cardiomyocytes deprived of oxygen, subsequent reperfusion of the ischemic tissue can lead to oxidative damage due to excessive generation of reactive oxygen species. Cardiomyocytes and their mitochondria are the main energy producers and consumers of the heart, and their metabolic changes during ischemia seem to be a key driver of reperfusion injury. Here, we hypothesized that tracking changes in cardiomyocyte metabolism, such as oxygen and ATP concentrations, would help in identifying points of metabolic failure during ischemia and reperfusion. To track some of these changes continuously from the onset of ischemia through reperfusion, we developed a system of differential equations representing the chemical reactions involved in the production and consumption of 67 molecular species. This model was validated and used to identify conditions present during periods of critical transition in ischemia and reperfusion that could lead to oxidative damage. These simulations identified a range of oxygen concentrations that lead to reverse mitochondrial electron transport at complex I of the respiratory chain and a spike in mitochondrial membrane potential, which are key suspects in the generation of reactive oxygen species at the onset of reperfusion. Our model predicts that a short initial reperfusion treatment with reduced oxygen content (5% of physiological levels) could reduce the cellular damage from both of these mechanisms. This model should serve as an open-source platform to test ideas for treatment of the ischemia reperfusion process by following the temporal evolution of molecular concentrations in the cardiomyocyte.

Molecular Signaling to Preserve Mitochondrial Integrity against Ischemic Stress in the Heart: Rescue or Remove Mitochondria in Danger

Cardiovascular diseases are one of the leading causes of death and global health problems worldwide, and ischemic heart disease is the most common cause of heart failure (HF). The heart is a high-energy demanding organ, and myocardial energy reserves are limited. Mitochondria are the powerhouses of the cell, but under stress conditions, they become damaged, release necrotic and apoptotic factors, and contribute to cell death. Loss of cardiomyocytes plays a significant role in ischemic heart disease. In response to stress, protective signaling pathways are activated to limit mitochondrial deterioration and protect the heart. To prevent mitochondrial death pathways, damaged mitochondria are removed by mitochondrial autophagy (mitophagy). Mitochondrial quality control mediated by mitophagy is functionally linked to mitochondrial dynamics. This review provides a current understanding of the signaling mechanisms by which the integrity of mitochondria is preserved in the heart against ischemic stress.

Regulation of STAT3 and its role in cardioprotection by conditioning: focus on non-genomic roles targeting mitochondrial function

Ischemia–reperfusion injury (IRI) is one of the biggest challenges for cardiovascular researchers given the huge death toll caused by myocardial ischemic disease. Cardioprotective conditioning strategies, namely pre- and post-conditioning maneuvers, represent the most important strategies for stimulating pro-survival pathways essential to preserve cardiac health. Conditioning maneuvers have proved to be fundamental for the knowledge of the molecular basis of both IRI and cardioprotection. Among this evidence, the importance of signal transducer and activator of transcription 3 (STAT3) emerged. STAT3 is not only a transcription factor but also exhibits non-genomic pro-survival functions preserving mitochondrial function from IRI. Indeed, STAT3 is emerging as an influencer of mitochondrial function to explain the cardioprotection phenomena. Studying cardioprotection, STAT3 proved to be crucial as an element of the survivor activating factor enhancement (SAFE) pathway, which converges on mitochondria and influences their function by cross-talking with other cardioprotective pathways. Clearly there are still some functional properties of STAT3 to be discovered. Therefore, in this review, we highlight the evidence that places STAT3 as a promoter of the metabolic network. In particular, we focus on the possible interactions of STAT3 with processes aimed at maintaining mitochondrial functions, including the regulation of the electron transport chain, the production of reactive oxygen species, the homeostasis of Ca²⁺ and the inhibition of opening of mitochondrial permeability transition pore. Then we consider the role of STAT3 and the parallels between STA3/STAT5 in cardioprotection by conditioning, giving emphasis to the human heart and confounders.

Preconditioning or Postconditioning with 8-Br-cAMP-AM Protects the Heart against Regional Ischemia and Reperfusion: A Role for Mitochondrial Permeability Transition

The cAMP analogue 8-Br-cAMP-AM (8-Br) confers marked protection against global ischaemia/reperfusion of isolated perfused heart. We tested the hypothesis that 8-Br is also protective under clinically relevant conditions (regional ischaemia) when applied either before ischemia or at the beginning of reperfusion, and this effect is associated with the mitochondrial permeability transition pore (MPTP). 8-Br (10 μM) was administered to Langendorff-perfused rat hearts for 5 min either before or at the end of 30 min regional ischaemia. Ca2+-induced mitochondria swelling (a measure of MPTP opening) and binding of hexokinase II (HKII) to mitochondria were assessed following the drug treatment at preischaemia. Haemodynamic function and ventricular arrhythmias were monitored during ischaemia and 2 h reperfusion. Infarct size was evaluated at the end of reperfusion. 8-Br administered before ischaemia attenuated ventricular arrhythmias, improved haemodynamic function, and reduced infarct size during ischaemia/reperfusion. Application of 8-Br at the end of ischaemia protected the heart during reperfusion. 8-Br promoted binding of HKII to the mitochondria and reduced Ca2+-induced mitochondria swelling. Thus, 8-Br protects the heart when administered before regional ischaemia or at the beginning of reperfusion. This effect is associated with inhibition of MPTP via binding of HKII to mitochondria, which may underlie the protective mechanism.

Interleukin 35 protects cardiomyocytes following ischemia/reperfusion-induced apoptosis via activation of mitochondrial STAT3

Mitochondrial reactive oxygen species (mtROS)-induced apoptosis has been suggested to contribute to myocardial ischemia/reperfusion injury. Interleukin 35 (IL-35), a novel anti-inflammatory cytokine, has been shown to protect the myocardium and inhibit mtROS production. However, its effect on cardiomyocytes upon exposure to hypoxia/reoxygenation (H/R) damage has not yet been elucidated. The present study aimed to investigate the potential protective role and underlying mechanisms of IL-35 in H/R-induced mouse neonatal cardiomyocyte injury. Mouse neonatal cardiomyocytes were challenged to H/R in the presence of IL-35, and we found that IL-35 dose dependently promotes cell viability, diminishes mtROS, maintains mitochondrial membrane potential, and decreases the number of apoptotic cardiomyocytes. Meanwhile, IL-35 remarkably activates mitochondrial STAT3 (mitoSTAT3) signaling, inhibits cytochrome c release, and reduces apoptosis signaling. Furthermore, co-treatment of the cardiomyocytes with the STAT3 inhibitor AG490 abrogates the IL-35-induced cardioprotective effects. Our study identified the protective role of IL-35 in cardiomyocytes following H/R damage and revealed that IL-35 protects cardiomyocytes against mtROS-induced apoptosis through the mitoSTAT3 signaling pathway during H/R.

Mitochondrial Biomarkers in Patients with ST-Elevation Myocardial Infarction and Their Potential Prognostic Implications: A Prospective Observational Study

Background: Mitochondrial biomarkers have been investigated in different critical settings, including ST-elevation myocardial infarction (STEMI). Whether they provide prognostic information in STEMI, complementary to troponins, has not been fully elucidated. We prospectively explored the in-hospital and long-term prognostic implications of cytochrome c and cell-free mitochondrial DNA (mtDNA) in STEMI patients undergoing primary percutaneous coronary intervention. Methods: We measured cytochrome c and mtDNA at admission in 466 patients. Patients were grouped according to mitochondrial biomarkers detection: group 1 (−/−; no biomarker detected; n = 28); group 2 (−/+; only one biomarker detected; n = 283); group 3 (+/+; both biomarkers detected; n = 155). A composite of in-hospital mortality, cardiogenic shock, and acute pulmonary edema was the primary endpoint. Four-year all-cause mortality was the secondary endpoint. Results: Progressively lower left ventricular ejection fractions (52 ± 8%, 49 ± 8%, 47 ± 9%; p = 0.006) and higher troponin I peaks (54 ± 44, 73 ± 66, 106 ± 81 ng/mL; p = 0.001) were found across the groups. An increase in primary (4%, 14%, 19%; p = 0.03) and secondary (10%, 15%, 23%; p = 0.02) endpoint rate was observed going from group 1 to group 3. The adjusted odds ratio increment of the primary endpoint from one group to the next was 1.65 (95% CI 1.04–2.61; p = 0.03), while the adjusted hazard ratio increment of the secondary endpoint was 1.55 (95% CI 1.12–2.52; p = 0.03). The addition of study group allocation to admission troponin I reclassified 12% and 22% of patients for the primary and secondary endpoint, respectively. Conclusions: Detection of mitochondrial biomarkers is common in STEMI and seems to be associated with in-hospital and long-term outcome independently of troponin.

Superior restoration of left ventricular performance after prolonged single-dose del Nido cardioplegia in conjunction with terminal warm blood cardioplegic reperfusion

OBJECTIVES

An incomplete restoration of left ventricular contractility after del Nido cardioplegia was noted in our recent study. This study tested the hypothesis that terminal warm blood cardioplegia promotes a prompt restoration of left ventricular performance after a prolonged single-dose del Nido cardioplegia.

METHODS

Fourteen piglets were subjected to 120 minutes of arrest by del Nido cardioplegia without terminal warm blood cardioplegia (del Nido cardioplegia group; n = 7) or with terminal warm blood cardioplegia before reperfusion (terminal warm blood cardioplegia group; n = 7). The other 7 piglets underwent total cardiopulmonary bypass without ischemia/reperfusion for 150 minutes (control group). Left ventricular function was assessed by percent recovery of end-systolic elastance as the contractility and percent end-diastolic pressure-volume relationship as the compliance using a conductance catheter. Troponin T and the mitochondrial score were also measured.

RESULTS

Depressed percent recovery of end-systolic elastance was sustained in the del Nido cardioplegia group, and a prompt restoration of end-systolic elastance was achieved using terminal warm blood cardioplegia (57.9 ± 17.8 vs 94.7 ± 13.1, P < .028). Percent end-diastolic pressure-volume relationship at the early phase was better in the terminal warm blood cardioplegia compared with the del Nido group (88.5 ± 24.0 vs 101.4 ± 16.8, P = .050). Troponin T was higher in the terminal warm blood cardioplegia compared with the control group (0.80% ± 0.21% and 1.49% ± 0.31%, respectively, P = .002). The mitochondrial score was equivalent in all groups. Spontaneous restoration to sinus rhythm was more frequent in the terminal warm blood cardioplegia group than in the del Nido cardioplegia group (6/7 vs 1/7, P < .028).

CONCLUSIONS

The supplementary use of terminal warm blood cardioplegia achieved prolongation of the safe ischemic time up to 120 minutes for a single-dose application.

Prostaglandin E1 attenuates post‑cardiac arrest myocardial dysfunction through inhibition of mitochondria‑mediated cardiomyocyte apoptosis

Post‑cardiac arrest myocardial dysfunction (PAMD) is a leading cause of death in patients undergoing resuscitation patients following cardiac arrest (CA). Although prostaglandin E1 (PGE1) is a clinical drug used to mitigate ischemia injury, its effect on PAMD remains unknown. In the present study, the protective effects of PGE1 on PAMD were evaluated in a rat model of CA and in a hypoxia‑reoxygenation (H/R) in vitro model. Rats were randomly assigned to CA, CA+PGE1 or sham groups. Asphyxia for 8 min followed by cardiopulmonary resuscitation were performed in the CA and CA+PGE1 groups. PGE1 was intravenously administered at the onset of return of spontaneous circulation (ROSC). PGE1 treatment significantly increased the ejection fraction and cardiac output within 4 h following ROSC and improved the survival rate, compared with the CA group. Moreover, PGE1 inactivated GSK3β, prevented mitochondrial permeability transition pore (mPTP) opening, while reducing cytochrome c and cleaved caspase‑3 expression, as well as cardiomyocyte apoptosis in the rat model. To examine the underlying mechanism, H/R H9c2 cells were treated with PGE1 at the start of reoxygenation. The changes in GSK3β activity, mPTP opening, cytochrome c and cleaved caspase‑3 expression, and apoptosis of H9c2 cells were consistent with those noted in vivo. The results indicated that PGE1 attenuated PAMD by inhibiting mitochondria‑mediated cardiomyocyte apoptosis.

Garlic Derived Diallyl Trisulfide in Experimental Metabolic Syndrome: Metabolic Effects and Cardioprotective Role

This study aimed to examine the effects of diallyl trisulfide (DATS), the most potent polysulfide derived from garlic, on metabolic syndrome and myocardial function in rats with metabolic syndrome (MetS). For that purpose, we used 36 male Wistar albino rats divided into control rats, rats with MetS and MetS rats treated with 40 mg/kg of DATS every second day for 3 weeks. In the first part, we studied the impact of DATS on MetS control and found that DATS significantly raised H₂S, decreased homocysteine and glucose levels and enhanced lipid and antioxidative, while reducing prooxidative parameters. Additionally, this polysulfide improved cardiac function. In the second part, we investigated the impact of DATS on ex vivo induced ischemia/reperfusion (I/R) heart injury and found that DATS consumption significantly improved cardiodynamic parameters and prevented oxidative and histo-architectural variation in the heart. In addition, DATS significantly increased relative gene expression of eNOS, SOD-1 and -2, Bcl-2 and decreased relative gene expression of NF-κB, IL-17A, Bax, and caspases-3 and -9. Taken together, the data show that DATS can effectively mitigate MetS and have protective effects against ex vivo induced myocardial I/R injury in MetS rat.

Activation of SIRT1/PGC 1α/SIRT3 pathway by melatonin provides protection against mitochondrial dysfunction in isoproterenol induced myocardial injury

AIMS

Preventing mitochondrial dysfunction and enhancing mitochondrial health and biogenesis is a crucial therapeutic approach to ameliorate injury following acute myocardial infarction. Although the antioxidant role of melatonin against ischemia/reperfusion injury has been reported, the exact mechanism of protection, in vivo, remains poorly understood. This study aims to identify and elaborate upon mechanism of melatonin protection of rat cardiac mitochondria against acute myocardial infarction.

MAIN METHODS

Rats were pre-treated with melatonin (10 mg/kg body weight (b.w.); intraperitoneally, i.p.) before isoproterenol bitartrate (ISO) administration (25 mg/kg body weight (b.w.) subcutaneously,s.c.) and their effect on rat heart mitochondrial structure and function was studied. Biochemical changes in activity of biomarkers of oxidative stress, antioxidant enzymes as well as Krebs' cycle enzymes were analyzed. Gene expression studies and Isothermal titration calorimetric studies with pure catalase and ISO were also carried out.

KEY FINDINGS

Melatonin was shown to reduce ISO induced oxidative stress, by stimulating superoxide dismutase activity and removing the inhibition of Krebs' cycle enzymes. Herein we report for the first time in rat model that melatonin activates the SIRT1-PGC-1α-SIRT3 signaling pathways after ISO administration, which ultimately induces mitochondrial biogenesis. Melatonin exhibited significant protection of mitochondrial architecture and topology along with increased calcium ion permeability and reactive oxygen species (ROS) generation induced by ISO. Isothermal calorimetric studies revealed that melatonin binds to ISO molecules and sequesters them from the reaction thereby limiting their interaction with catalase along with occupying the binding sites of catalase themselves.

SIGNIFICANCE

Activation of SIRT1-PGC-1α-SIRT3 pathway by melatonin along with its biophysical properties prevents ISO induced mitochondrial injury in rat heart.

Mechanism of Hydrogen Sulfide Preconditioning-Associated Protection Against Ischemia-Reperfusion Injury Differs in Diabetic Heart That Develops Myopathy

Hydrogen sulfide (H₂S) is reported to be effective in the management of the myocardial ischemia-reperfusion (I/R) injury via PI3K/GSK3β pathway in normal rats. However, its efficacy against I/R in the presence of diabetic cardiomyopathy is relatively obscure. Thus, the present work aimed to find out H₂S-mediated cardioprotection against I/R in diabetic cardiomyopathy and to evaluate its mode of action using Langendorff isolated heart perfusion system. The present work includes three groups of rat, viz. (i) normal, (ii) diabetes mellitus (DM: streptozotocin: 35 mg/kg; normal diet), and (iii) diabetes + high-fat diet (DCM) (streptozotocin: 35 mg/kg; high-fat diet). The effect of NaHS (an H₂S donor; 20 µM) on cardiac function in isolated rat hearts demonstrates that H₂S preconditioning (HIPC) significantly attenuated myocardial injury in both DM and DCM hearts, as evidenced by the (i) improvement in hemodynamics, which includes rate pressure product [(in mmHg × 10³× bpm) DM: 40 to 56; DCM: 21 to 58] and left ventricular developed pressure [(in mmHg) DM: 53 to 74; DCM: 28 to 74), (ii) reduction in infarct size (25% to 8%) and attenuated caspase activity, compared to their respective I/R controls. Also, the observed positive recovery of mitochondrial function during HIPC treatment reinforces the cardioprotection by HIPC in DCM heart against I/R injury. However, HIPC could not repair I/R-induced oxidative stress in DCM rat heart. Further, to study the H₂S mode of action, the experimental rats were exposed to a PI3K inhibitor (Wortmannin) and GSK3β inhibitor (SB216763) before HIPC protocol, whose results suggest that unlike in normal and DM, HIPC mediates its cardioprotective effect independent of PI3K/GSK3β pathway. To conclude, HIPC ameliorates I/R injury in DCM rat via an alternative pathway other than existing PI3K pathway, which is required to be probed under disease conditions.

The Rationale of Neprilysin Inhibition in Prevention of Myocardial Ischemia-Reperfusion Injury during ST-Elevation Myocardial Infarction

During the last three decades, timely myocardial reperfusion using either thrombolytic therapy or primary percutaneous intervention (pPCI) has allowed amazing improvements in outcomes with a more than halving in 1-year ST-elevation myocardial infarction (STEMI) mortality. However, mortality and left ventricle (LV) remodeling remain substantial in these patients. As such, novel therapeutic interventions are required to reduce myocardial infarction size, preserve LV systolic function, and improve survival in reperfused-STEMI patients. Myocardial ischemia-reperfusion injury (MIRI) prevention represents the main goal to reach in order to reduce STEMI mortality. There is currently no effective therapy for MIRI prevention in STEMI patients. A significant reason for the weak and inconsistent results obtained in this field may be the presence of multiple, partially redundant, mechanisms of cell death during ischemia-reperfusion, whose relative importance may depend on the conditions. Therefore, it is always more recognized that it is important to consider a "multi-targeted cardioprotective therapy", defined as an additive or synergistic cardioprotective agents or interventions directed to distinct targets with different timing of application (before, during, or after pPCI). Given that some neprilysin (NEP) substrates (natriuretic peptides, angiotensin II, bradykinin, apelins, substance P, and adrenomedullin) exert a cardioprotective effect against ischemia-reperfusion injury, it is conceivable that antagonism of proteolytic activity by this enzyme may be considered in a multi-targeted strategy for MIRI prevention. In this review, by starting from main pathophysiological mechanisms promoting MIRI, we discuss cardioprotective effects of NEP substrates and the potential benefit of NEP pharmacological inhibition in MIRI prevention.

Myocardial ischaemia-reperfusion injury and cardioprotection in perspective

Despite the increasing use and success of interventional coronary reperfusion strategies, morbidity and mortality from acute myocardial infarction are still substantial. Myocardial infarct size is a major determinant of prognosis in these patients. Therefore, cardioprotective strategies aim to reduce infarct size. However, a perplexing gap exists between the many preclinical studies reporting infarct size reduction with mechanical and pharmacological interventions and the poor translation into better clinical outcomes in patients. This Review revisits the pathophysiology of myocardial ischaemia-reperfusion injury, including the role of autophagy and forms of cell death such as necrosis, apoptosis, necroptosis and pyroptosis. Other cellular compartments in addition to cardiomyocytes are addressed, notably the coronary microcirculation. Preclinical and clinical research developments in mechanical and pharmacological approaches to induce cardioprotection, and their signal transduction pathways, are discussed. Additive cardioprotective interventions are advocated. For clinical translation into treatments for patients with acute myocardial infarction, who typically are of advanced age, have comorbidities and are receiving several medications, not only infarct size reduction but also attenuation of coronary microvascular obstruction, as well as longer-term targets including infarct repair and reverse remodelling, must be considered to improve patient outcomes. Future clinical trials must focus on patients who really need adjunct cardioprotection, that is, those with severe haemodynamic alterations.

Novel Findings and Therapeutic Targets on Cardioprotection of Ischemia/ Reperfusion Injury in STEMI

Acute ST-segment elevation myocardial infarction (STEMI) remains a leading cause of morbidity and mortality around the world. A large number of STEMI patients after the infarction gradually develop heart failure due to the infarcted myocardium. Timely reperfusion is essential to salvage ischemic myocardium from the infarction, but the restoration of coronary blood flow in the infarct-related artery itself induces myocardial injury and cardiomyocyte death, known as ischemia/reperfusion injury (IRI). The factors contributing to IRI in STEMI are complex, and microvascular obstruction, inflammation, release of reactive oxygen species, myocardial stunning, and activation of myocardial cell death are involved. Therefore, additional cardioprotection is required to prevent the heart from IRI. Although many mechanical conditioning procedures and pharmacological agents have been identified as effective cardioprotective approaches in animal studies, their translation into the clinical practice has been relatively disappointing due to a variety of reasons. With new emerging data on cardioprotection in STEMI over the past few years, it is mandatory to reevaluate the effectiveness of "old" cardioprotective interventions and highlight the novel therapeutic targets and new treatment strategies of cardioprotection.

Modified Del Nido Cardioplegia and Its Evaluation in a Piglet Model

Del Nido cardioplegia (DN) is not available worldwide as the required solution is made from a commercial base (PlasmaLyte) that is not approved in all countries. We report our own modified DN solution and confirm its safety and effectiveness. Fourteen piglets were subjected to 90 minutes of global ischemia on cardiopulmonary bypass induced by original DN (n = 7) or NS (normal saline)-based DN (n = 7). Our DN solution begins with a base of NS (800 mL) and distilled water (200 mL), to which are added 15 mL KCl (2 mEq/mL), 17 mL NaHCO₃ (1 mEq/mL), 10 mL MgSO₄ (0.2 g/mL), 13 mL lidocaine 1%, and 13 mL mannitol 25%. LV function recovery was assessed in end-systolic elastance (EES) as systolic function and end-diastolic pressure-volume relationship (EDPVR) as diastolic function using a conductance catheter. Creatine kinase-MB (CK-MB) and mitochondrial score were also measured. Left ventricular (LV) contractility after ischemia (%EES ± SD) was not significantly different between the group induced by original DN (89.3 ± 20.6%) and the group induced by NS-based DN (99.3 ± 18.4%). LV compliance (%EDPVR ± SD) was likewise not significantly different between these groups (102.7 ± 28.2% vs 94.4 ± 22.8%, PL vs NS, respectively). CK-MB was equivalent between the groups. Mitochondrial scores were not significantly different between the groups, and this difference did not cause severe damage. NS-based DN preserves LV function recovery after prolonged global ischemia as effectively and as safely as original DN does. NS-based modified DN can be substituted for original DN.

Translational issues for mitoprotective agents as adjunct to reperfusion therapy in patients with ST-segment elevation myocardial infarction

Pre‐clinical studies have indicated that mitoprotective drugs may add cardioprotection beyond rapid revascularization, antiplatelet therapy and risk modification. We review the clinical efficacy of mitoprotective drugs that have progressed to clinical testing comprising cyclosporine A, KAI‐9803, MTP131 and TRO 40303. Whereas cyclosporine may reduce infarct size in patients undergoing primary angioplasty as evaluated by release of myocardial ischaemic biomarkers and infarct size imaging, the other drugs were not capable of demonstrating this effect in the clinical setting. The absent effect leaves the role of the mitochondrial permeability transition pore for reperfusion injury in humans unanswered and indicates that targeting one single mechanism to provide mitoprotection may not be efficient. Moreover, the lack of effect may relate to favourable outcome with current optimal therapy, but conditions such as age, sex, diabetes, dyslipidaemia and concurrent medications may also alter mitochondrial function. However, as long as the molecular structure of the pore remains unknown and specific inhibitors of its opening are lacking, the mitochondrial permeability transition pore remains a target for alleviation of reperfusion injury. Nevertheless, taking conditions such as ageing, sex, comorbidities and co‐medication into account may be of paramount importance during the design of pre‐clinical and clinical studies testing mitoprotective drugs.

Ozone alleviates ischemia/reperfusion injury by inhibiting mitochondrion-mediated apoptosis pathway in SH-SY5Y cells

Cerebral ischemia/reperfusion (I/R) injuries are common and often cause severe complications. Ozone has been applied for protecting I/R injury in animal models of several organs including cerebra, but the detailed mechanism remains unclear. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and lactate dehydrogenase measurement were used to determine the influence of ozone on cell activity and damage of SH-SY5Y cells. Some redox items such as catalase (CAT), malondialdehyde (MDA), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) were measured by enzyme-linked immunosorbent assay. The mitochondrial membrane potential (ΔΨ_m ) was determined by JC-1 assay. Cytochrome-c (cyt-c) level in the cytoplasm and mitochondrion was measured by western blotting. Apoptosis was determined by flow cytometry, and some apoptosis-related molecules were detected by quantitative real-time polymerase chain reaction and western blotting. Ozone alleviated oxidative damage by increasing GSH-Px, SOD, CAT, and decreasing MDA. Ozone decreased mitochondrial damage caused by I/R injury and inhibited the release of cyt-c from mitochondrion to cytoplasm in SH-SY5Y cells. The cell apoptosis caused by I/R was inhibited by ozone, and ozone could decrease apoptosis by increasing the ratio of Bcl-2/Bax and inhibiting caspase signaling pathway in SH-SY5Y cells. Ozone has the ability of maintaining redox homeostasis, decreasing mitochondrion damage, and inhibiting neurocytes apoptosis induced by I/R. Therefore, ozone may be a promising protective strategy against cerebral I/R injury.

Exogenous 10 kDa-Heat Shock Protein Preserves Mitochondrial Function After Hypoxia/Reoxygenation

Humoral factors released during ischemic preconditioning (IPC) protect the myocardium against ischemia/reperfusion (I/R) injury. We have recently identified 10 kDa-heat shock protein (HSP10) and a fraction of small 5-10 kDa peptides (5-10-sP) in the coronary effluent of IPC-treated hearts and demonstrated their cardioprotective potential. We here used our isolated mitochondria model to characterize the impact of exogenous HSP10 and 5-10-sP on mitochondria function from myocardium subjected to I/R injury. Isolated perfused rat hearts were submitted to 30-min global ischemia and 10-min reperfusion. Before ischemia, isolated hearts were infused with saline or 5-10-sP, with or without a mitochondrial ATP-sensitive-K⁺-channel blocker (5HD 10 μmol·L^-1) or PKC inhibitor (chelerythrine 10 μmol·L^-1), before I/R. HSP10 (1 µmol·L^-1) was infused into isolated hearts before I/R without blockers. At 10-min reperfusion, the mitochondria were isolated and mitochondrial function was assessed. In a subset of experiments, freshly isolated mitochondria were directly incubated with HSP10 or 5-10-sP with or without 5HD or chelerythrine before in vitro hypoxia/reoxygenation. Infusion of 5-10-sP (n = 5) and HSP10 (n = 5) into isolated hearts before I/R improved mitochondrial ADP-stimulated respiration, ATP production and prevented mitochondrial ROS formation compared to the I/R group (n = 5); this effect was abrogated by 5HD and chelerythrine. In freshly isolated mitochondria with in vitro hypoxia/reoxygenation, HSP10 (n = 16) and 5-10-sP (n = 16) incubation prevented reductions of mitochondrial ADP-stimulated respiration (91.5 ± 5.1 nmol O2/min/mg PTN), ATP production (250.1 ± 9.3 μmol ATP/200μg PTN), and prevented mitochondrial ROS production (219.7 ± 9.0 nmol H2O2/200μg PTN) induced by hypoxia/reoxygenation (n = 12, 51.5 ± 5.0 nmol O2/min/mg PTN; 187 ± 21.7 μmol ATP/200 μg PTN; 339.0 ± 14.3 nmol H2O2/200 μg PTN, p < 0.001, respectively). 5HD reduced the ADP-stimulated respiration in the HSP10 group (65.84 ± 3.3 nmol O2/min/mg PTN), ATP production (193.7 ± 12.1 μmol ATP/200μg PTN) and increased ROS in the 5-10-sP group (274.4 ± 21.7 nmol H2O2/200 μg PTN). Mitochondria are a target of the cardioprotection induced by 5-10-sP and HSP10. This protection is dependent of PKC and mK_ATP activation. HSP10 can act directly on mitochondria and protects against hypoxia/reoxygenation injury by mK_ATP activation.

Cardiac protective effects of remote ischaemic preconditioning in children undergoing tetralogy of fallot repair surgery: a randomized controlled trial

Aims

Remote ischaemic preconditioning (RIPC) by inducing brief ischaemia in distant tissues protects the heart against myocardial ischaemia-reperfusion injury (IRI) in children undergoing open-heart surgery, although its effectiveness in adults with comorbidities is controversial. The effectiveness and mechanism of RIPC with respect to myocardial IRI in children with tetralogy of Fallot (ToF), a severe cyanotic congenital cardiac disease, undergoing open heart surgery are unclear. We hypothesized that RIPC can confer cardioprotection in children undergoing ToF repair surgery.

Methods and results

Overall, 112 ToF children undergoing radical open cardiac surgery using cardiopulmonary bypass (CPB) were randomized to either a RIPC group (n = 55) or a control group (n = 57). The RIPC protocol consisted of three cycles of 5-min lower limb occlusion and 5-min reperfusion using a cuff-inflator. Serum inflammatory cytokines and cardiac injury markers were measured before surgery and after CPB. Right ventricle outflow tract (RVOT) tissues were collected during the surgery to assess hypoxia-inducible factor (Hif)-1α and other signalling proteins. Cardiac mitochondrial injury was assessed by electron microscopy. The primary results showed that the length of stay in the intensive care unit (ICU) was longer in the control group than in the RIPC group (52.30 ± 13.43 h vs. 47.55 ± 10.34 h, respectively, P = 0.039). Patients in the control group needed longer post-operative ventilation time compared to the RIPC group (35.02 ± 6.56 h vs. 31.96 ± 6.60 h, respectively, P = 0.016). The levels of post-operative serum troponin-T at 12 and 18 h, CK-MB at 24 h, as well as the serum h-FABP levels at 6 h, after CPB were significantly lower, which was coincident with significantly higher protein expression of cardiac Hif-1α, p-Akt, p-STAT3, p-STAT5, and p-eNOS and less vacuolization of mitochondria in the RIPC group compared to the control group.

Conclusion

In ToF children undergoing open heart surgery, RIPC attenuates myocardial IRI and improves the short-term prognosis.

Chloride channel blocker IAA-94 increases myocardial infarction by reducing calcium retention capacity of the cardiac mitochondria

Indanyloxyacetic acid-94 (IAA-94), an intracellular chloride channel blocker, is shown to ablate cardioprotection rendered by ischemic preconditioning (IPC), N (6)-2-(4-aminophenyl) ethyladenosine or the PKC activator phorbol 12-myristate 13-acetate and cyclosporin A (CsA) in both ex-vivo and in-vivo ischemia-reperfusion (IR) injury. Thus signifying the role of the IAA-94 sensitive chloride channels in mediating cardio-protection upon IR injury. Although IAA-94 sensitive chloride currents are recorded in cardiac mitoplast, there is still a lack of understanding of the mechanism by which IAA-94 increases myocardial infarction (MI) by IR injury. Mitochondria are the key arbitrators of cell life and death pathways. Both oxidative stress and calcium overload in the mitochondria, elicit pathways resulting in the opening of mitochondrial permeability transition pore (mPTP) leading to cell death. Therefore, in this study we explored the role of IAA-94 in MI and in maintaining calcium retention capacity (CRC) of cardiac mitochondria after IR. IAA-94 inhibited the CRC of the isolated cardiac mitochondria in a concentration-dependent manner as measured spectrofluorimetrically using calcium green-5 N. Interestingly, IAA-94 did not change the mitochondrial membrane potential. Further, CsA a blocker of mPTP opening could not override the effect of IAA-94. We also showed for the first time that IAA-94 perfusion after ischemic event augments MI by reducing the CRC of mitochondria. To conclude, our results demonstrate that the mechanism of IAA-94 mediated cardio-deleterious effects is via modulating the mitochondria CRC, thereby playing a role in mPTP opening. These findings highlight new pharmacological targets, which can mediate cardioprotection from IR injury.

Cyclocreatine protects against ischemic injury and enhances cardiac recovery during early reperfusion

Introduction: A critical mechanism of how hypoxia/ischemia causes irreversible myocardial injury is through the exhaustion of adenosine triphosphate (ATP). Cyclocreatine (CCr) and its water-soluble salt Cyclocreatine-Phosphate (CCrP) are potent bioenergetic agents that preserve high levels of ATP during ischemia. Areas covered: CCr and CCrP treatment prior to the onset of ischemia, preserved high levels of ATP in ischemic myocardium, reduced myocardial cell injury, exerted anti-inflammatory and anti-apoptotic activities, and restored contractile function during reperfusion in animal models of acute myocardial infarction (AMI), global cardiac arrest, cardiopulmonary bypass, and heart transplantation. Medline and Embase (1970 - Feb 2019), the WIPO databank (up to Feb 2019); no language restriction. Expert opinion: This review provides the basis for a number of clinical applications of CCrP and CCr to minimize ischemic injury and necrosis. One strategy is to administer CCrP to AMI patients in the pre-hospital phase, as well as during, or after Percutaneous Coronary Intervention (PCI) procedure to potentially achieve protection of the myocardium, reduce infarcted-size, and, thus, limit the progression to heart failure. Another clinical applications are in predictable myocardial ischemia where pretreatment with CCrP would likely improve outcome and quality of life of patients who will undergo cardiopulmonary bypass for coronary revascularization and end-stage heart failure patients scheduled for heart transplantation.

Cardioprotection of Tetrahedral DNA Nanostructures in Myocardial Ischemia-Reperfusion Injury

Acute myocardial infarction, which can be extremely difficult to treat, is the worst deadly disease around the world. Reperfusion is expedient to reverse myocardial ischemia. However, during reperfusion, reactive oxygen species (ROS) produced by myocardial ischemia-reperfusion injury (MIRI) and further cell apoptosis are the most serious challenges to cardiomyocytes. Therefore, searching for reagents that can simultaneously reduce oxidative damage and MIRI-induced apoptosis is the pivotal strategy to rescue injured cardiomyocytes. Nevertheless, current cardioprotective drugs have some shortcomings, such as cardiotoxicity, inadequate intravenous administration, or immature technology. Previous studies have shown that tetrahedral DNA nanostructures (TDNs) have biological safety with promising anti-inflammatory and antioxidative potential. However, the progress that TDNs have made in the biological behavior of cardiomyocytes has not been explored. In this experiment, a cellular model of MIRI was first established. Then, confirmed by a series of experiments, our study indicates that TDNs can significantly decrease oxidative damage and apoptosis by limiting the overexpression of ROS, along with effecting the expression of apoptosis-related proteins. In addition, Western blot analysis demonstrated that TDNs could activate the Akt/Nrf2 signaling pathway to improve the myocardial injury induced by MIRI. Above all, the antioxidant and antiapoptotic capacities of TDNs make them a potential therapeutic drug for MIRI. This study provides new ideas and directions for more homogeneous diseases induced by oxidative damage.

Excellent Restoration of Left Ventricular Compliance After Prolonged Del Nido Single-Dose Cardioplegia in an In Vivo Piglet Model

Del Nido cardioplegia (DN) is used in congenital heart surgery and recently in adults, a single dose has been administered. However, the tolerable ischemic time has not been established. The objective is to evaluate the left ventricular (LV) function recovery and accompanying biochemical and histologic markers to clarify the tolerable ischemic time in an in vivo cardiopulmonary bypass (CPB) piglet model. Twenty-one piglets were subjected to either 90 minutes (with or without topical cooling; TC) or 120 minutes (with TC) of global ischemia induced by single-dose DN, while the other 7 served as the control group (CPB only). The CPB temperature was established with a perfusion temperature of 30°C. The LV function recovery was assessed by the percent change in end-systolic elastance (Ees) and the end-diastolic pressure-volume relationship (EDPVR). Creatine kinase-MB (CK-MB) levels and the mitochondrial score were also assessed. LV contractility assessed by %Ees after 90 and 120 minutes of ischemia (89.3 ± 20.6% and 57.9 ± 17.8%) was lower compared with the control group (122.6 ± 35.8%, P = 0.001). Conversely, LV compliance assessed by %EDPVR was preserved in both groups (102.7 ± 28.2% and 88.5 ± 24.0%), which was comparable to the control group (105.8 ± 36.9%, P = 0.531). There was no change in LV contractility after 90 minutes of ischemia with or without TC (89.3 ± 20.6% or 84.8 ± 16.2%, P = 0.657), whereas LV compliance was lower but not statistically different without TC (102.7 ± 28.2% vs 78.0 ± 38.9%). CK-MB and the mitochondrial score were equivalent between all groups. The proposed single-dose ischemic time for redosing is 90 minutes using TC.

Traditional Chinese Medicine for Coronary Heart Disease: Clinical Evidence and Possible Mechanisms

Coronary heart disease (CHD) remains a major cause of mortality with a huge economic burden on healthcare worldwide. Here, we conducted a systematic review to investigate the efficacy and safety of Chinese herbal medicine (CHM) for CHD based on high-quality randomized controlled trials (RCTs) and summarized its possible mechanisms according to animal-based researches. 27 eligible studies were identified in eight database searches from inception to June 2018. The methodological quality was assessed using seven-item checklist recommended by Cochrane Collaboration. All the data were analyzed using Rev-Man 5.3 software. As a result, the score of study quality ranged from 4 to 7 points. Meta-analyses showed CHM can significantly reduce the incidence of myocardial infarction and percutaneous coronary intervention, and cardiovascular mortality (P < 0.05), and increase systolic function of heart, the ST-segment depression, and clinical efficacy (P < 0.05). Adverse events were reported in 11 studies, and CHMs were well tolerated in patients with CHD. In addition, CHM exerted cardioprotection for CHD, possibly altering multiple signal pathways through anti-inflammatory, anti-oxidation, anti-apoptosis, improving the circulation, and regulating energy metabolism. In conclusion, the evidence available from present study revealed that CHMs are beneficial for CHD and are generally safe.

The valosin-containing protein protects the heart against pathological Ca2+ overload by modulating Ca2+ uptake proteins

Stress-induced mitochondrial calcium (Ca2+) overload is a key cellular toxic effectors and a trigger of cardiomyocyte death during cardiac ischemic injury through the opening of mitochondrial permeability transition pore (mPTP). We previously found that the valosin-containing protein (VCP), an ATPase-associated protein, protects cardiomyocytes against stress-induced death and also inhibits mPTP opening in vitro. However, the underlying molecular mechanisms are not fully understood. Here, we tested our hypothesis that VCP acts as a novel regulator of mitochondrial Ca2+ uptake proteins and resists cardiac mitochondrial Ca2+ overload by modulating mitochondrial Ca2+ homeostasis. By using a cardiac-specific transgenic (TG) mouse model in which VCP is overexpressed by 3.5 folds in the heart compared to the wild type (WT) mouse, we found that, under the pathological extra-mitochondrial Ca2+ overload, Ca2+ entry into cardiac mitochondria was reduced in VCP TG mice compared to their little-matched WT mice, subsequently preventing mPTP opening and ATP depletion under the Ca2+ challenge. Mechanistically, overexpression of VCP in the heart resulted in post-translational protein degradation of the mitochondrial Ca2+ uptake protein 1 (MICU1), an activator of the mitochondria Ca2+ uniporter (MCU) that is responsible for mitochondrial calcium uptake. Together, our results reveal a new regulatory role of VCP in cardiac mitochondrial Ca2+ homeostasis and unlock the potential mechanism by which VCP confers its cardioprotection.

Optimized Treatment of ST-Elevation Myocardial Infarction

Primary percutaneous coronary intervention is nowadays the preferred reperfusion strategy for patients with acute ST-segment-elevation myocardial infarction, aiming at restoring epicardial infarct-related artery patency and achieving microvascular reperfusion as early as possible, thus limiting the extent of irreversibly injured myocardium. Yet, in a sizeable proportion of patients, primary percutaneous coronary intervention does not achieve effective myocardial reperfusion due to the occurrence of coronary microvascular obstruction (MVO). The amount of infarcted myocardium, the so-called infarct size, has long been known to be an independent predictor for major adverse cardiovascular events and adverse left ventricular remodeling after myocardial infarction. Previous cardioprotection studies were mainly aimed at protecting cardiomyocytes and reducing infarct size. However, several clinical and preclinical studies have reported that the presence and extent of MVO represent another important independent predictor of adverse left ventricular remodeling, and recent evidences support the notion that MVO may be more predictive of major adverse cardiovascular events than infarct size itself. Although timely and complete reperfusion is the most effective way of limiting myocardial injury and subsequent ventricular remodeling, the translation of effective therapeutic strategies into improved clinical outcomes has been largely disappointing. Of importance, despite the presence of a large number of studies focused on infarct size, only few cardioprotection studies addressed MVO as a therapeutic target. In this review, we provide a detailed summary of MVO including underlying causes, diagnostic techniques, and current therapeutic approaches. Furthermore, we discuss the hypothesis that simultaneously addressing infarct size and MVO may help to translate cardioprotective strategies into improved clinical outcome following ST-segment-elevation myocardial infarction.

Effects of metformin on the heart with ischaemia-reperfusion injury: Evidence of its benefits from in vitro, in vivo and clinical reports

Ischaemia reperfusion (I/R) injury following myocardial infarction reperfusion therapy is a phenomenon that results in further loss of cardiomyocytes and cardiac contractility. Among the potential therapeutics to counter cardiac I/R injury, the antidiabetic drug metformin has shown promising experimental results. This review encompasses evidence available from studies of metformin's protective effects on the heart following cardiac I/R in vitro, ex vivo and in vivo, alongside clinical trials. Experimental data describes potential mechanisms of metformin, including activation of AMPK, an energy sensing kinase with many downstream effects. Suggested effects include upregulation of superoxide dismutases (SODs), which reduce oxidative stress and improve mitochondrial function. Additionally, metformin demonstrates anti-apoptotic effects, most likely by inhibiting mitochondrial permeability transition pore (mPTP) opening, and anti-inflammatory effects, by JNK inhibition. Recent reports of metformin's role in modulating complex I activity of the electron transport chain following cardiac I/R are also presented and discussed. Furthermore, clinical reports present mixed findings, suggesting that beneficial effects may depend on dosage, timing and condition of patients receiving metformin treatment. Conclusively there is an increased need for prospective, placebo-controlled clinical studies to confirm the mechanisms and to demonstrate that metformin is a suitable and safe drug for treatment of cardiac I/R injury.

Hydroxysafflor Yellow A mitigated myocardial ischemia/reperfusion injury by inhibiting the activation of the JAK2/STAT1 pathway

Hydroxysafflor Yellow A (HSYA) may reduce ischemia/reperfusion (I/R) injury. However, the underlying molecular mechanisms remain unclear. The present study explored the effect and the mechanisms of HSYA on myocardial injury in vivo and in vitro. Myocardial infarct size was assessed by Evans blue/2,3,5‑triphenyltetrazoliumchloride staining. Levels of cardiac troponin I (cTnI), interleukin‑6 (IL‑6), lactate dehydrogenase (LDH), superoxide dismutase (SOD) and malondialdehyde (MDA) were measured using commercial kits. Alteration of mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) generation was determined by fluorescent signals. Apoptosis was detected by terminal deoxynucleotidyl‑transferase‑mediated dUTP nick‑end labeling staining, flow cytometry assay and caspase‑3 activity. Expression levels of the apoptosis‑associated proteins were detected by reverse transcription quantitative polymerase chain reaction and western blot analysis. In vivo, animals treated with HSYA presented less severe myocardial injury and decreased janus kinase 2 (JAK2)/signal transducer and activator of transcription 1 (STAT1) activity, improved antioxidant capacity and decreased apoptosis. In vitro, compared with the hypoxia (H)/reoxygenation (R) + HSYA group, AG490 and S1491 treatment decreased the releases of cTnI, IL‑6 and LDH and enhanced the resistance to oxidative stress by maintaining MMP and decreasing ROS generation. In addition, AG490 and S1491 were also identified to alleviate the H/R‑induced apoptosis by inhibiting caspase 3 activity and modulating the expression levels of cleaved caspase‑3, tumor necrosis factor receptor superfamily member 6 (Fas), Fas ligand, B‑cell lymphoma 2 (Bcl‑2) and Bcl‑2‑associated X protein. These data suggested that inactivation of the JAK2/STAT1 pathway strengthened the HSYA‑induced protective effect in H/R‑induced myocardial injury. In conclusion, the treatment of HSYA was effective in decreasing IR‑induced myocardial injury, and this may be largely dependent on the JAK2/STAT1 pathway. Therefore, the present study provided a potential strategy to prevent myocardial I/R injury.

Different adaptive NO-dependent Mechanisms in Normal and Hypertensive Conditions

Myocardial infarction (MI) remains the leading cause of death worldwide. We aimed to investigate the effect of NO deficiency on selective biochemical parameters within discreet myocardial zones after experimentally induced MI. To induce MI, the left descending coronary artery was ligated in two groups of 16-week-old WKY rats. In one group, NO production was inhibited by L-NAME (20 mg/kg/day) administration four weeks prior to ligation. Sham operations were performed on both groups as a control. Seven days after MI, we evaluated levels of nitric oxide synthase (NOS) activity, eNOS, iNOS, NFҡB/p65 and Nrf2 in ischemic, injured and non-ischemic zones of the heart. Levels of circulating TNF-α and IL-6 were evaluated in the plasma. MI led to increased NOS activity in all investigated zones of myocardium as well as circulating levels of TNF-α and IL-6. L-NAME treatment decreased NOS activity in the heart of sham operated animals. eNOS expression was increased in the injured zone and this could be a compensatory mechanism that improves the perfusion of the myocardium and cardiac dysfunction. Conversely, iNOS expression increased in the infarcted zone and may contribute to the inflammatory process and irreversible necrotic changes.

Targeting autophagy in cardiac ischemia/reperfusion injury: A novel therapeutic strategy

Acute myocardial infarction (AMI) is one of the leading causes of morbidity worldwide. Myocardial reperfusion is known as an effective therapeutic choice against AMI. However, reperfusion of blood flow induces ischemia/reperfusion (I/R) injury through different complex processes including ion accumulation, disruption of mitochondrial membrane potential, the formation of reactive oxygen species, and so forth. One of the processes that gets activated in response to I/R injury is autophagy. Indeed, autophagy acts as a "double-edged sword" in the pathology of myocardial I/R injury and there is a controversy about autophagy being beneficial or detrimental. On the basis of the autophagy effect and regulation on myocardial I/R injury, many studies targeted it as a therapeutic strategy. In this review, we discuss the role of autophagy in I/R injury and its targeting as a therapeutic strategy.